Are MXenes Promising Anode Materials for Li Ion Batteries? Computational Studies on Electronic Properties and Li Storage Capability of Ti₃C₂ and Ti₃C₂X₂ (X = F, OH) Monolayer

Abstract

Density functional theory (DFT) computations were performed to investigate the electronic properties and Li storage capability of Ti(3)C(2), one representative MXene (M represents transition metals, and X is either C or/and N) material, and its fluorinated and hydroxylated derivatives. The Ti(3)C(2) monolayer acts as a magnetic metal, while its derived Ti(3)C(2)F(2) and Ti(3)C(2)(OH)(2) in their stable conformations are semiconductors with small band gaps. Li adsorption forms a strong Coulomb interaction with Ti(3)C(2)-based hosts but well preserves its structural integrity. The bare Ti(3)C(2) monolayer exhibits a low barrier for Li diffusion and high Li storage capacity (up to Ti(3)C(2)Li(2) stoichiometry). The surface functionalization of F and OH blocks Li transport and decreases Li storage capacity, which should be avoided in experiments. The exceptional properties, including good electronic conductivity, fast Li diffusion, low operating voltage, and high theoretical Li storage capacity, make Ti(3)C(2) MXene a promising anode material for Li ion batteries.

Intercalation and delamination of layered carbides and carbonitrides

“…S7, the 410 mA h g À 1 represents three Li per Ti 3 C 2 (OH) 2 . The capacity obtained at 1C was higher than the maximum theoretical capacity of f-Ti 3 C 2 MXene predicted by Tang et al 25 using DFT (320 mA h g À 1 ), although the as-delaminated d-MXenes have OH and F on the surface that theoratically reduce the reversible capacity. The reason for this mismatch is unclear at this time.…”

“…A recent computational study 25 concluded that d-Ti 3 C 2 layers would be attractive for Li-ion battery anodes. To date, our Li-ion work was carried out on stacked multilayer particles 23,24 .…”

“…They also are good electrical conductors [17][18][19][20][21] and are predicted to have high elastic moduli. 22 Electrochemical intercalation of Li ions between the MXene sheets renders these solids promising materials for Liion battery anodes and hybrid electrochemical capacitors [23][24][25] . However, up to now there have been no reports of the chemical intercalation or large-scale delamination of MXenes or any other transition metal carbides.…”

“…The original aim of this work was to reduce the f-Ti 3 C 2 surfaces to create Ti-terminated surfaces that theory predicts would be magnetic 25 . A perusal of the graphene literature made it clear that hydrazine monohydrate N 2 H 4 Á H 2 O (HM) dissolved in N,Ndimethylformamide (DMF) is the reactant of choice 26 .…”

Transition Metal‐Promoted V2CO2 (MXenes): A New and Highly Active Catalyst for Hydrogen Evolution Reaction

“…Shortly after the synthesis of MXenes,12 their possible application as anode materials for Li ion batteries (LIBs) has been explored greatly and these MXenes exhibit good capability for high charge–discharge rates 14, 17, 18, 19. Besides LIBs, other applications, such as non‐Li‐ion batteries,20, 21 hydrogen storage,22, 23 supercapacitor,24 and thermoelectric materials,25 have also been investigated.…”